Page last updated at 09:29 GMT, Wednesday, 6 August 2008 10:29 UK

Quakes caught by laptop sensor

People wait outside during LA earthquake
The recent quake in LA was captured by the network

A device originally put into laptops to prevent damage to the hard drive if the machine is dropped has been put to a novel use by scientists.

The tiny devices that detect unexpected movement are being used to give warnings on earthquakes.

The Quakecatcher Network has been built by combining the readings of sensors in laptops known as accelerometers.

It successfully detected last month's quake in Los Angeles.

Jesse Lawrence, assistant professor of geophysics at Stanford University and colleagues from the University of California Riverside, told BBC World Service's Digital Planet programme that accelerometers are perfect for monitoring earthquakes.

In the case of laptops, the accelerometer detects when the machine has been knocked off a desk or dropped. Before impact the heads on the hard drive are pulled clear of the platters where data is stored to prevent physical damage.

"When you accidentally knock your laptop off the desk, the accelerometer is detecting a large, strong new motion," he said.


Currently the system is iin its early stages with only three laptops fully connected.

While an individual machine "can't necessarily tell the difference" between a quake and someone just getting up quickly and knocking their laptop forcefully, Dr Lawrence explained the key is the number of machines networked together.

"If there's just a few of them, then the server will know it's just people knocking their laptops around accidentally," he said.

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"But if we're flooded with a large number of triggers, then we'll know that there is a large, significant earthquake in the area."

The sensitivity is variable, depending on distance from the quake.

Once movement is detected, the information is sent to the server, where it is verified as to whether it is an earthquake.

Although this may only provide a few moments' warning, every second counts in such a situation.

"If it is an earthquake, we could potentially send out signals to those who need it even before the energy from the quake has expanded out from the epicentre to those other people," Dr Lawrence said.

"In California, we train pupils in schools to jump underneath desks when there's an earthquake drill.

"We can do the same thing in all sorts of varieties of situations, and those few seconds can count."

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